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class="fa-fw fas fa-heart"></i><span> 关于</span></a></div></div><div id="toggle-menu"><a class="site-page"><i class="fas fa-bars fa-fw"></i></a></div></div></nav><div id="post-info"><h1 class="post-title">Chapter 4: Expressions</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2022-05-14T06:24:59.000Z" title="发表于 2022-05-14 14:24:59">2022-05-14</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2022-05-14T06:53:53.689Z" title="更新于 2022-05-14 14:53:53">2022-05-14</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/blog/categories/C/">C++</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-commentcount"><i class="far fa-comments fa-fw post-meta-icon"></i><span class="post-meta-label">评论数:</span><a href="/blog/2022/05/14/Chapter-4-Expressions/#post-comment" itemprop="discussionUrl"><span class="valine-comment-count" data-xid="/blog/2022/05/14/Chapter-4-Expressions/" itemprop="commentCount"></span></a></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><p>﻿# Exercises Section 4.1.2</p>
<h2 id="Ex4-1"><a href="#Ex4-1" class="headerlink" title="Ex4.1"></a>Ex4.1</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">5</span> + <span class="number">10</span> * <span class="number">20</span> / <span class="number">2</span> = <span class="number">105</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-2"><a href="#Ex4-2" class="headerlink" title="Ex4.2"></a>Ex4.2</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">a) *(vec.<span class="built_in">begin</span>())</span><br><span class="line">b) (*(vec.<span class="built_in">begin</span>())) + <span class="number">1</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-2"><a href="#Exercises-Section-4-2" class="headerlink" title="Exercises Section 4.2"></a>Exercises Section 4.2</h1><h2 id="Ex4-4"><a href="#Ex4-4" class="headerlink" title="Ex4.4"></a>Ex4.4</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">((<span class="number">12</span> / <span class="number">3</span>) * <span class="number">4</span>) + (<span class="number">5</span> * <span class="number">15</span>) + ((<span class="number">24</span> % <span class="number">4</span>) / <span class="number">2</span>) = <span class="number">91</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-5"><a href="#Ex4-5" class="headerlink" title="Ex4.5"></a>Ex4.5</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a) <span class="number">-30</span> * <span class="number">3</span> + <span class="number">21</span> / <span class="number">5</span> = <span class="number">-86</span></span><br><span class="line">b) <span class="number">-30</span> + <span class="number">3</span> * <span class="number">21</span> / <span class="number">5</span> = <span class="number">-18</span></span><br><span class="line">c) <span class="number">30</span> / <span class="number">3</span> * <span class="number">21</span> % <span class="number">5</span> = <span class="number">0</span></span><br><span class="line">d) <span class="number">-30</span> / <span class="number">3</span> * <span class="number">21</span> % <span class="number">4</span> = <span class="number">-2</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-6"><a href="#Ex4-6" class="headerlink" title="Ex4.6"></a>Ex4.6</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;iostream&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="type">int</span> value;</span><br><span class="line">    cin &gt;&gt; value;</span><br><span class="line">    <span class="keyword">if</span> (value % <span class="number">2</span> == <span class="number">0</span>)</span><br><span class="line">        cout &lt;&lt; <span class="string">&quot;The number is even &quot;</span> &lt;&lt; endl;</span><br><span class="line">    <span class="keyword">else</span> </span><br><span class="line">        cout &lt;&lt; <span class="string">&quot;The number is odd&quot;</span> &lt;&lt; endl;</span><br><span class="line">    <span class="built_in">system</span>(<span class="string">&quot;pause&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-7"><a href="#Ex4-7" class="headerlink" title="Ex4.7"></a>Ex4.7</h2><p><img src="https://img-blog.csdnimg.cn/2021052716504599.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MTcwMzE3NA==,size_16,color_FFFFFF,t_70#pic_center" alt="在这里插入图片描述"></p>
<h1 id="Exercises-Section-4-3"><a href="#Exercises-Section-4-3" class="headerlink" title="Exercises Section 4.3"></a>Exercises Section 4.3</h1><h2 id="Ex4-9"><a href="#Ex4-9" class="headerlink" title="Ex4.9"></a>Ex4.9</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">const</span> <span class="type">char</span> *cp = <span class="string">&quot;Hello World&quot;</span>;</span><br><span class="line"><span class="keyword">if</span> (cp &amp;&amp; *cp)	<span class="comment">// 如果指针 cp 的内容不为 0 且指针  cp 指向的地址内的内容不为 0，那么条件成立</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-10"><a href="#Ex4-10" class="headerlink" title="Ex4.10"></a>Ex4.10</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;iostream&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="type">int</span> value;</span><br><span class="line">    <span class="keyword">while</span> ((cin &gt;&gt; value) &amp;&amp; (value != <span class="number">42</span>))</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; value &lt;&lt; <span class="string">&quot; &quot;</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    cout &lt;&lt; endl;</span><br><span class="line">    <span class="built_in">system</span>(<span class="string">&quot;pause&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-11"><a href="#Ex4-11" class="headerlink" title="Ex4.11"></a>Ex4.11</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;iostream&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">void</span> <span class="title">test</span><span class="params">(<span class="type">int</span> a, <span class="type">int</span> b, <span class="type">int</span> c, <span class="type">int</span> d)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="keyword">if</span> ((a &gt; b) &amp;&amp; (b &gt; c) &amp;&amp; (c &gt; d))</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; <span class="string">&quot;Success&quot;</span> &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> </span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; <span class="string">&quot;Failed&quot;</span> &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="type">int</span> a, b, c, d;</span><br><span class="line">    cout &lt;&lt; <span class="string">&quot;Please enter four numbers: &quot;</span> &lt;&lt; endl;</span><br><span class="line">    cin &gt;&gt; a &gt;&gt; b &gt;&gt; c &gt;&gt; d;</span><br><span class="line">    <span class="built_in">test</span>(a, b, c, d);</span><br><span class="line">    <span class="built_in">system</span>(<span class="string">&quot;pause&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-12"><a href="#Ex4-12" class="headerlink" title="Ex4.12"></a>Ex4.12</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> i, j, k;</span><br><span class="line"><span class="keyword">if</span> (i != j &lt; k) 	<span class="comment">// 如果 j &lt; k 那么就判断 i 是否等于 1，不等于则条件成立；	如果 j &gt;= k 那么就判断 i 是否等于 0，不等于则条件成立</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-4"><a href="#Exercises-Section-4-4" class="headerlink" title="Exercises Section 4.4"></a>Exercises Section 4.4</h1><h2 id="Ex4-13"><a href="#Ex4-13" class="headerlink" title="Ex4.13"></a>Ex4.13</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> i;	<span class="type">double</span> d;</span><br><span class="line">a) d = i = <span class="number">3.5</span>;		<span class="comment">// i = 3, d = 3.0</span></span><br><span class="line">b) i = d = <span class="number">3.5</span>;		<span class="comment">// d = 3.5, i = 3</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-14"><a href="#Ex4-14" class="headerlink" title="Ex4.14"></a>Ex4.14</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> (<span class="number">42</span> = i)		<span class="comment">// 非法，42不能为左值</span></span><br><span class="line"><span class="keyword">if</span> (i = <span class="number">42</span>) 	<span class="comment">// 合法，变量 i 被赋值42，条件一直成立</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-15"><a href="#Ex4-15" class="headerlink" title="Ex4.15"></a>Ex4.15</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">double</span> dval; <span class="type">int</span> ival; <span class="type">int</span> *pi;</span><br><span class="line">dval = ival = pi = <span class="number">0</span>;	<span class="comment">// int double 类型都不能和指针类型发生转换</span></span><br><span class="line"><span class="comment">// 修改如下：</span></span><br><span class="line">dval = ival = *pi = <span class="number">0</span>;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-16"><a href="#Ex4-16" class="headerlink" title="Ex4.16"></a>Ex4.16</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">a) <span class="keyword">if</span> (p = <span class="built_in">getPtr</span>() != <span class="number">0</span>)	<span class="comment">// origin</span></span><br><span class="line">   <span class="keyword">if</span> ((p = <span class="built_in">getPtr</span>()) != <span class="number">0</span>)	<span class="comment">// 修改</span></span><br><span class="line">   </span><br><span class="line">b) <span class="keyword">if</span> (i = <span class="number">1024</span>)	<span class="comment">// origin</span></span><br><span class="line">   <span class="keyword">if</span> (i == <span class="number">1024</span>) 	<span class="comment">// 修改</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-5"><a href="#Exercises-Section-4-5" class="headerlink" title="Exercises Section 4.5"></a>Exercises Section 4.5</h1><h2 id="Ex4-17"><a href="#Ex4-17" class="headerlink" title="Ex4.17"></a>Ex4.17</h2><p>前缀增量符例如 “++i”，先增加变量 i 的值然后再使用 i 的值；后缀增量符例如 “i++”先使用变量 i 然后再把 i 的值加1。而且后缀增量符会创建一个临时变量，效率没有相同效果的前缀增量符高。</p>
<h2 id="Ex4-18"><a href="#Ex4-18" class="headerlink" title="Ex4.18"></a>Ex4.18</h2><p>如果使用了前缀增量符会超出 vector 容器容量。</p>
<h2 id="Ex4-19"><a href="#Ex4-19" class="headerlink" title="Ex4.19"></a>Ex4.19</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> *ptr;	vector&lt;<span class="type">int</span>&gt; vec;	<span class="type">int</span> ival;</span><br><span class="line"></span><br><span class="line">a) ptr != <span class="number">0</span> &amp;&amp; *ptr++	<span class="comment">// 指针 ptr 内容不为 0 且指针 ptr 指向的地址的内容不为 0 条件成立，判断后增加 ptr 的值</span></span><br><span class="line"></span><br><span class="line">b) ival++ &amp;&amp; ival	<span class="comment">// 可能是不正确的</span></span><br><span class="line">   ++ival &amp;&amp; ival 	<span class="comment">// 修改</span></span><br><span class="line">   </span><br><span class="line">c) vec[ival++] &lt;= vec[ival]		<span class="comment">// 可能是不正确的</span></span><br><span class="line">   vec[++ival] &lt;= vec[ival]		<span class="comment">//  修改</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-6"><a href="#Exercises-Section-4-6" class="headerlink" title="Exercises Section 4.6"></a>Exercises Section 4.6</h1><h2 id="Ex4-20"><a href="#Ex4-20" class="headerlink" title="Ex4.20"></a>Ex4.20</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">vector&lt;string&gt;::iterator iter;</span><br><span class="line">a) *iter++;		<span class="comment">// 合法</span></span><br><span class="line">b) (*iter)++;	<span class="comment">// 非法； 修改：*iter++</span></span><br><span class="line">c) *iter.<span class="built_in">empty</span>()	<span class="comment">// 非法；   修改：(*iter).empty()</span></span><br><span class="line">d) iter-&gt;<span class="built_in">empty</span>()	<span class="comment">// 合法</span></span><br><span class="line">e) ++*iter;			<span class="comment">// 非法；修改：*iter++</span></span><br><span class="line">f) iter++-&gt;<span class="built_in">empty</span>();	<span class="comment">// 合法</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-7"><a href="#Exercises-Section-4-7" class="headerlink" title="Exercises Section 4.7"></a>Exercises Section 4.7</h1><h2 id="Ex4-21"><a href="#Ex4-21" class="headerlink" title="Ex4.21"></a>Ex4.21</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;iostream&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;vector&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    <span class="type">int</span> value;</span><br><span class="line">    vector&lt;<span class="type">int</span>&gt; vec;</span><br><span class="line">    <span class="keyword">while</span> (cin &gt;&gt; value)</span><br><span class="line">    &#123;</span><br><span class="line">        vec.<span class="built_in">push_back</span>(value);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">for</span> (<span class="keyword">auto</span> it = vec.<span class="built_in">begin</span>(); it != vec.<span class="built_in">end</span>(); ++it)</span><br><span class="line">    &#123;</span><br><span class="line">        <span class="keyword">if</span> (*it % <span class="number">2</span> == <span class="number">0</span>)</span><br><span class="line">            cout &lt;&lt; *it &lt;&lt; <span class="string">&quot; is even&quot;</span> &lt;&lt; endl;</span><br><span class="line">        <span class="keyword">else</span> </span><br><span class="line">            cout &lt;&lt; *it &lt;&lt; <span class="string">&quot; is odd&quot;</span> &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="built_in">system</span>(<span class="string">&quot;pause&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-23"><a href="#Ex4-23" class="headerlink" title="Ex4.23"></a>Ex4.23</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">string s = <span class="string">&quot;word&quot;</span>;</span><br><span class="line">string p1 = s + s[s.<span class="built_in">size</span>() - <span class="number">1</span>] == <span class="string">&#x27;s&#x27;</span> ? <span class="string">&quot;&quot;</span> : <span class="string">&quot;s&quot;</span>;	<span class="comment">// 类型不匹配</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 修改如下</span></span><br><span class="line">string p1 = s + (s[s.<span class="built_in">size</span>() - <span class="number">1</span>] == <span class="string">&#x27;s&#x27;</span> ? <span class="string">&quot;&quot;</span> : <span class="string">&quot;s&quot;</span>);</span><br><span class="line"></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-8"><a href="#Exercises-Section-4-8" class="headerlink" title="Exercises Section 4.8"></a>Exercises Section 4.8</h1><h2 id="Ex4-25"><a href="#Ex4-25" class="headerlink" title="Ex4.25"></a>Ex4.25</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="string">&#x27;q&#x27;</span>  --&gt; <span class="number">01110001</span></span><br><span class="line">~<span class="string">&#x27;q&#x27;</span> --&gt; <span class="number">10001110</span></span><br><span class="line">(~<span class="string">&#x27;q&#x27;</span> &lt;&lt; <span class="number">6</span>) --&gt; <span class="number">10000000</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-27"><a href="#Ex4-27" class="headerlink" title="Ex4.27"></a>Ex4.27</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">unsigned</span> <span class="type">long</span> ul1 = <span class="number">3</span>, ul2 = <span class="number">7</span>;</span><br><span class="line">a) ul1 &amp; ul2	<span class="comment">// 3</span></span><br><span class="line">b) ul1 | ul2 	<span class="comment">// 7</span></span><br><span class="line">c) ul1 &amp;&amp; ul2 	<span class="comment">// true</span></span><br><span class="line">d) ul1 || ul2	<span class="comment">// true</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-9"><a href="#Exercises-Section-4-9" class="headerlink" title="Exercises Section 4.9"></a>Exercises Section 4.9</h1><h2 id="Ex4-28"><a href="#Ex4-28" class="headerlink" title="Ex4.28"></a>Ex4.28</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span><span class="string">&lt;iostream&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="type">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">char</span>) &lt;&lt; endl;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">short</span>) &lt;&lt; endl;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">int</span>) &lt;&lt; endl;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">long</span>) &lt;&lt; endl;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">float</span>) &lt;&lt; endl;</span><br><span class="line">    cout &lt;&lt; <span class="built_in">sizeof</span>(<span class="type">double</span>) &lt;&lt; endl;</span><br><span class="line">    <span class="built_in">system</span>(<span class="string">&quot;pause&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-29"><a href="#Ex4-29" class="headerlink" title="Ex4.29"></a>Ex4.29</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> x[<span class="number">10</span>];	<span class="type">int</span> *p = x;</span><br><span class="line">cout &lt;&lt; <span class="built_in">sizeof</span>(x) / <span class="built_in">sizeof</span>(*x) &lt;&lt; endl;		<span class="comment">// 结果为 10</span></span><br><span class="line">cout &lt;&lt; <span class="built_in">sizeof</span>(p) / <span class="built_in">sizeof</span>(*p) &lt;&lt; endl;		<span class="comment">// 结果为 2</span></span><br></pre></td></tr></table></figure>

<h2 id="Ex4-30"><a href="#Ex4-30" class="headerlink" title="Ex4.30"></a>Ex4.30</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a) <span class="built_in">sizeof</span>(x + y)</span><br><span class="line">b) <span class="built_in">sizeof</span>(p-&gt;mem[i])</span><br><span class="line">c) <span class="built_in">sizeof</span>(a) &lt; b</span><br><span class="line">d) <span class="built_in">sizeof</span>(<span class="built_in">f</span>())</span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-10"><a href="#Exercises-Section-4-10" class="headerlink" title="Exercises Section 4.10"></a>Exercises Section 4.10</h1><h2 id="Ex4-32"><a href="#Ex4-32" class="headerlink" title="Ex4.32"></a>Ex4.32</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 分别用指针和索引遍历数组</span></span><br><span class="line"><span class="keyword">constexpr</span> <span class="type">int</span> size = <span class="number">5</span>;</span><br><span class="line"><span class="type">int</span> ia[size] = &#123;<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>&#125;;</span><br><span class="line"><span class="keyword">for</span> (<span class="type">int</span> *ptr = ia, ix = <span class="number">0</span>; ix != size &amp;&amp; ptr != ia + size; ++ix, ++ptr)	&#123;   <span class="comment">/*... */</span> &#125;</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-33"><a href="#Ex4-33" class="headerlink" title="Ex4.33"></a>Ex4.33</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 如果someValue 为真，那么 x 加 1，y 加 1；反之，x 减 1，y 减 1</span></span><br><span class="line">someValue ? ++x, ++y : --x, --y;</span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Section-4-11-1"><a href="#Exercises-Section-4-11-1" class="headerlink" title="Exercises Section 4.11.1"></a>Exercises Section 4.11.1</h1><h2 id="Ex4-35"><a href="#Ex4-35" class="headerlink" title="Ex4.35"></a>Ex4.35</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">char</span> cval;	<span class="type">int</span> ival;	<span class="type">unsigned</span> <span class="type">int</span> ui;</span><br><span class="line"><span class="type">float</span> fval;	<span class="type">double</span> dval;</span><br><span class="line"></span><br><span class="line">a) cval = <span class="string">&#x27;a&#x27;</span> + <span class="number">3</span>;	<span class="comment">// 结果为 d</span></span><br><span class="line">b) fval = ui - ival * <span class="number">1.0</span>;	<span class="comment">// ival 从 int 转换成 float, ui 从 unsigned int 转换成 float</span></span><br><span class="line">c) dval = ui * fval;	<span class="comment">// ui 转换成 float，最后结果再转换成 double </span></span><br><span class="line">d) cval = ival + fval + dval;	<span class="comment">// 先是 ival 转换成 float 类型，然后 (ival + fval) 转换成 double 类型，最后结果转换为 char 类型</span></span><br></pre></td></tr></table></figure>

<h1 id="Exercises-Scetion-4-11-3"><a href="#Exercises-Scetion-4-11-3" class="headerlink" title="Exercises Scetion 4.11.3"></a>Exercises Scetion 4.11.3</h1><h2 id="Ex4-36"><a href="#Ex4-36" class="headerlink" title="Ex4.36"></a>Ex4.36</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> i = <span class="number">2</span>;</span><br><span class="line"><span class="type">double</span> d = <span class="number">3.5</span>;</span><br><span class="line">i *= <span class="built_in">static_cast</span>&lt;<span class="type">int</span>&gt;(d);</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-37"><a href="#Ex4-37" class="headerlink" title="Ex4.37"></a>Ex4.37</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> i; <span class="type">double</span> d; <span class="type">const</span> string *ps;	<span class="type">char</span> *pc; <span class="type">void</span> *pv;</span><br><span class="line"></span><br><span class="line">a) pv = (<span class="type">void</span>*)ps;</span><br><span class="line">b) i = (<span class="type">int</span>)(*pc);	---&gt;   i = <span class="built_in">static_cast</span>&lt;<span class="type">int</span>&gt;(*pc);</span><br><span class="line">c) pv = &amp;d;		   ---&gt;   pv = <span class="built_in">static_cast</span>&lt;<span class="type">void</span>*&gt;(&amp;d);</span><br><span class="line">d) pc = (<span class="type">char</span>*) pv;   ---&gt;   pc = <span class="built_in">static_cast</span>&lt;<span class="type">char</span>*&gt;(pv);</span><br></pre></td></tr></table></figure>

<h2 id="Ex4-38"><a href="#Ex4-38" class="headerlink" title="Ex4.38"></a>Ex4.38</h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 将变量 j 除以 变量 i 的值转换成 double 类型赋给 变量 slope</span></span><br><span class="line"><span class="type">double</span> slope = <span class="built_in">static_cast</span>&lt;<span class="type">double</span>&gt;(j / i);</span><br></pre></td></tr></table></figure>
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class="social-icon" href="mailto:a842181471@qq.com.com" target="_blank" title="Email"><i class="fas fa-envelope"></i></a></div></div><div class="card-widget card-announcement"><div class="item-headline"><i class="fas fa-bullhorn fa-shake"></i><span>公告</span></div><div class="announcement_content">朝九晚五，健康生活！</div></div><div class="sticky_layout"><div class="card-widget" id="card-toc"><div class="item-headline"><i class="fas fa-stream"></i><span>目录</span><span class="toc-percentage"></span></div><div class="toc-content"><ol class="toc"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-1"><span class="toc-number">1.</span> <span class="toc-text">Ex4.1</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-2"><span class="toc-number">2.</span> <span class="toc-text">Ex4.2</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-2"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.2</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-4"><span class="toc-number">1.</span> <span class="toc-text">Ex4.4</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-5"><span class="toc-number">2.</span> <span class="toc-text">Ex4.5</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-6"><span class="toc-number">3.</span> <span class="toc-text">Ex4.6</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-7"><span class="toc-number">4.</span> <span class="toc-text">Ex4.7</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-3"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.3</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-9"><span class="toc-number">1.</span> <span class="toc-text">Ex4.9</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-10"><span class="toc-number">2.</span> <span class="toc-text">Ex4.10</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-11"><span class="toc-number">3.</span> <span class="toc-text">Ex4.11</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-12"><span class="toc-number">4.</span> <span class="toc-text">Ex4.12</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-4"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.4</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-13"><span class="toc-number">1.</span> <span class="toc-text">Ex4.13</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-14"><span class="toc-number">2.</span> <span class="toc-text">Ex4.14</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-15"><span class="toc-number">3.</span> <span class="toc-text">Ex4.15</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-16"><span class="toc-number">4.</span> <span class="toc-text">Ex4.16</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-5"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.5</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-17"><span class="toc-number">1.</span> <span class="toc-text">Ex4.17</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-18"><span class="toc-number">2.</span> <span class="toc-text">Ex4.18</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-19"><span class="toc-number">3.</span> <span class="toc-text">Ex4.19</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-6"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.6</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-20"><span class="toc-number">1.</span> <span class="toc-text">Ex4.20</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-7"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.7</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-21"><span class="toc-number">1.</span> <span class="toc-text">Ex4.21</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-23"><span class="toc-number">2.</span> <span class="toc-text">Ex4.23</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-8"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.8</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-25"><span class="toc-number">1.</span> <span class="toc-text">Ex4.25</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-27"><span class="toc-number">2.</span> <span class="toc-text">Ex4.27</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-9"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.9</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-28"><span class="toc-number">1.</span> <span class="toc-text">Ex4.28</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-29"><span class="toc-number">2.</span> <span class="toc-text">Ex4.29</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-30"><span class="toc-number">3.</span> <span class="toc-text">Ex4.30</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-10"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.10</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-32"><span class="toc-number">1.</span> <span class="toc-text">Ex4.32</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-33"><span class="toc-number">2.</span> <span class="toc-text">Ex4.33</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Section-4-11-1"><span class="toc-number"></span> <span class="toc-text">Exercises Section 4.11.1</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-35"><span class="toc-number">1.</span> <span class="toc-text">Ex4.35</span></a></li></ol></li><li class="toc-item toc-level-1"><a class="toc-link" href="#Exercises-Scetion-4-11-3"><span class="toc-number"></span> <span class="toc-text">Exercises Scetion 4.11.3</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-36"><span class="toc-number">1.</span> <span class="toc-text">Ex4.36</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-37"><span class="toc-number">2.</span> <span class="toc-text">Ex4.37</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#Ex4-38"><span class="toc-number">3.</span> <span class="toc-text">Ex4.38</span></a></li></ol></div></div><div class="card-widget card-recent-post"><div class="item-headline"><i class="fas fa-history"></i><span>最新文章</span></div><div class="aside-list"><div class="aside-list-item no-cover"><div class="content"><a class="title" href="/blog/2022/05/17/%E3%80%8A%E7%AE%97%E6%B3%95%E8%AE%BE%E8%AE%A1%E6%89%8B%E5%86%8C%E3%80%8B%E9%9D%A2%E8%AF%95%E9%A2%98%EF%BC%9AChapter-1/" title="《算法设计手册》面试题：Chapter 1">《算法设计手册》面试题：Chapter 1</a><time datetime="2022-05-17T07:35:05.000Z" title="发表于 2022-05-17 15:35:05">2022-05-17</time></div></div><div class="aside-list-item no-cover"><div class="content"><a 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